Zinc plating process and electrolytes therefor

ABSTRACT

This invention relates to a method of producing bright zinc electrodeposits over a wide current density range, free of &#39;&#39;&#39;&#39;spores&#39;&#39;&#39;&#39; and/or striations, which comprises passing current from an anode to a metal cathode for a time period sufficient to deposit a bright zinc electrodeposit upon said cathode; the current passing through an aqueous bath composition containing at least one zinc compound providing zinc ions for electroplating zinc, A. AT LEAST ONE BATH SOLUBLE SURFACTANT SELECTED FROM THE GROUP CONSISTING OF BATH SOLUBLE POLYETHERS, SUBSTITUTED POLYETHERS, AND SUBSTITUTED NON-AROMATIC NITROGEN HETEROCYCLIC SURFACTANTS, AND B. AT LEAST ONE AROMATIC, NON-CARBONYL CONTAINING NITROGEN HETEROCYCLIC COMPOUND.

United States Patent n91 Habulak ZINC PLATING PROCESS AND ELECTROLYTESTHEREFOR [75] Inventor: Edward Paul Habulak, Allen Park.

Mich.

[73] Assignee: M & T Chemicals Inc., Greenwich.

Conn.

[22 Filed: Dec. 5, I973 [21] Appl. No.: 421.923

Related US. Application Data [62] Division of Ser. No. 293.659. Sept.36. 1972. Pat.

No. 3.82l.095.

[52} U.S. Cl 204/55 R [5 l I Int. Cl. CZSD 3/22 {58] Field of Search204/55 R, 55 Y. 43 Z, 44

[56] References Cited UNITED STATES PATENTS 3.296105 H1967 Rushmere104/55 Y 3.318.787 5/[967 Rindt r r t r .4 204/55 Y 3.787.297 l/l974Beckwith et al. r 204/55 R 3.823.076 7/l974 Rushmerc 204/55 R [451 Nov.1 1, 1975 Primary Exumr'nerG. L. Kaplan Altar/w). Age/1!. mFirml'\'enneth G. WheeleSS: Robert P. Auher [57] ABSTRACT This inventionrelates to a method of producing bright zinc electrodeposits over a widecurrent density range. free of spores and/or striations. which comprisespassing current from an anode to a metal cathode for a time periodsufficient to deposit a bright zinc elec trodeposit upon said cathode;the current passing through an aqueous hath composition containing atleast one zinc compound providing zinc ions for elec troplating zinc.

a. at least one bath soluble surfactant selected from the groupconsisting of bath soluble polyethers. substituted polyethers. andsubstituted non-aromatic nitrogen heterocyclic surfactants. and

b. at least one aromatic. non-carbonyl containing nitrogen hcterocycliccompound.

38 Claims. N0 Drawings ZINC PLATING PROCESS AND ELECTROLYTES THEREFORThis application is a divisional application of copending applicationSer. No. 293,659 filed September 26 1972 and now US. Pat. No. 3821,7095

This invention relates to the electrodeposition of bright zinc, and isespecially useful for plating from non-cyanide baths. More particularlythis invention relates to improved zinc plating bath compositions, tomethods of using and preparing such bath compositions and to improvedsurfaces having bright zinc electrodeposits thereon.

The enactment and enforcement of various environmental protection laws,especially those designed to improve water quality, have made itdesirable to significantly reduce or eliminate the discharge ofcyanides, phosphates, and a number of metal ions from the effluents ofelectroplating plants. As a result, non-polluting bright zinc platingprocesses have been sought as alternatives to the classical zinc cyanidebaths.

Alkaline solutions containing complex compounds of zinc and alkalinemetal pyrophosphates have been proposed as a replacement for cyanidebaths and cyanide processes for the electrodeposition of bright zinc.The electrodeposition of zinc using a pyrophosphate bath, however, maygive relatively poor low current density coverage, spore formation,roughness, insufficient brightness, and relatively non-uniform deposits.In addition, passivation of the anodes may produce undesirableprecipitates which in turn can clog filter systems and sometimes resultsin intermittent operation necessitated by frequent changes of filtermedia.

The use of phosphates may also produce waste disposal problems sincephosphates are not easily re moved and may promote the growth ofundesirable aquatic plant life if discharged into streams. Thesedisposal disadvantages further limit the acceptance of pyrophosphatezinc plating bath compositions in industrial applications.

Non-cyanide zincate zinc plating baths have also been proposed assubstitutes for cyanide containing systems. However, the bright platingcurrent density range of these baths is quite limited, making theplating of articles of complex shape difficult, if not impossible. Sincethe addition of cyanide to these non-cyanide zincate baths greatlyimproves the bright plate current density range of the deposits, platerstend to add cyanides to their zincate systems, thus negating thenoncyanide feature of the original bath.

Highly acidic zinc plating baths have been known for some time and suchbaths are cyanide-free. These systems do not produce bright decorativedeposits, (in the currently accepted usage of the word bright), haveextremely poor low current density coverage and find their chiefapplication in the strip line plating of wire and sheet steel using veryhigh but narrow current density ranges. Thus, they are not suited forplating objects of complex shape or for nonnal decorative, orrustproofing application.

More recently, neutral, mildly alkaline or mildly acidic non-cyanidezinc plating baths containing large amounts of buffering and complexingagents to stabilize both pH and solubilize the zinc ions at the pHvalues involved have been employed to overcome the objections of usingcyanide-based zinc plating processes. in general these zinc bathsconsist of an aqueous solu- LII tion containing at least one simple zincsalt, (for example zinc sulfate, zinc chloride, zinc acetate), and anammonium salt (for example an ammonium halide, or ammonium sulfate). Thezinc bath may additionally contain an organic zinc complexing agent suchas a hydroxy carboxylic acid or salts thereof, ethylenediaminetetraacetic acid or salts thereof, and/or similar materials to preventthe precipitation of zinc from the bath as the insoluble hydroxide athigher values of pH, i.e. pH 5.5 and above. These baths are typicallyoperated in the pH range of about 4 to 8.

Additions of suitable bath soluble surfactants such as polyoxyalkylenecompounds to zinc baths of the foregoing type may result in improvedthrowing power, hardness, and luster of the zinc deposits. Arepresentative bath composition may consist of:

ZnCl 50 g/l NH,C l I25 g/l Citric Acid 60 g/l NH,OH to adjust the pH tosome value between e.g. 4 and 8.

Suitable bath soluble polyoxyalkylene surfactant 6 g/] in order toimprove and increase the brightness, luster and throwing power of zincdeposits from these baths, certain organic aromatic carbonyl compoundsare generally used as brighteners. While these brighteners providegenerally satisfactory zinc deposits from freshly prepared zinc baths,the deposits tend to be dull in low current density regions. Inaddition, because of the nature of the aromatic organic additives usedas brighteners, highly objectionable oily decomposition products mayform on prolonged bath electrolysis. These oily materials are notsoluble in the bath and float on the surface where they adhere to partsas they are placed in and removed from the bath causing pitting problemsduring the plating cycle, with blotching and non-unifon'n results insubsequent chromate posttreatment of the zinc deposits. Removal of theseoily decomposition products is difficult and troublesome, and as aresult zinc electroplating processes of this type have found onlylimited acceptance in the plating industry.

While mildly acidic, neutral, and/or mildly basic zinc plating baths ofthe type described above have the potential for producing suitablebright zinc deposits, the inclusion in their composition of organiccomplexing agents such as hydroxy carboxylic acids, and/or saltsthereof, ethylenediamine tetraacetic acid and/or salts fl'iereof, aswell as other complexing agents makes it extremely difficult andexpensive to remove zinc metal ions from these electroplating bath wasteeffluents. As a result, in the current state of the art of bright zincelectroplating from non-cyanide zinc baths, the use of organiccomplexing agents is avoided.

The exclusion of organic metal complexing agents from bright zincelectroplating baths has made it possible to effectively and easilyremove zinc metal ions from plating plant waste efiluents in compliancewith anti-pollution laws. However, with the elimination of organiccomplexing agents it is desirable to operate the zinc bath in the mildlyacidic pH range, and it is more difficult to produce satisfactory brightzinc deposits over a wide current density range from these complexfreebaths using the previously effective bath additives.

Additionally, the deposits from these baths are generally severelystriated and/or covered with spores in the medium and high currentdensity areas. Spores can best be described as very small, discrete,frosty-looking mounds, possibly an unique type of bumt deposit, oftenaccompanied by gas pitting, and completely unacceptable in bright zincdeposits.

It is an object of this invention to provide novel processes andcompositions for the electrodeposition of bright to brilliant zincplate, over a wide current density range, especially from mildly acidic,neutral, or mildly alkaline zinc plating baths, which may or may notadditionally contain organic complexing agents; said deposits being freeof objectionable spores and/or striations. Other objects of theinvention will be apparent to those skilled in the art of bright zincplating upon inspection of the following detailed description.

This invention relates to a method of producing bright to brilliant zincelectrodeposits over a wide current density range, free of spores and/orstriations, which comprises passing current from an anode to a metalcathode for a time period sufficient to deposit a bright zincelectrodeposit upon said cathode; the current passing through an aqueousbath composition containing at least one zinc compound providing zincions for electroplating zinc, a suitable bath-soluble surfactant as asupport or carrier and at least one compound selected from the class ofcompounds consisting of aromatic noncarbonyl nitrogen heterocycles. Thefollowing generalized fonnulae describe typical compounds falling withinthe scope of this invention:

l x N Y a l X Y [1 Y n Z wherein each R is independently hydrogen,alkyl, alkenyl, alkoxy, alkylamine, alkysulfonic acid and/or saltthereof, sulfonic acid and/or salt thereof, halogen, amine, hydroxyl,mercapto, nitn'le, benzyl, or phenylalkyl (where m is an integer 0 to4); n is an integer 0 to 3; R is a divalent alkylene, divalentalkeneylene, secondary amine, or a direct bond between two heterocyclicrings; R" is a bifunctional radical such as z is O or i; Y is oxygen,allyl, propargyl, benzyl, an alk oxy group, alkyl sulfonic acid-(CH,),,-SO (where p is an integer of from l to 4), an oxyalkylsulfonicacid, quinaldinyl, halogenated alkeneyl radicals such as and the radicalp-phenoxybenzyl and X provides ionic charge neutrality where necessaryand represents an anionic radical or the anionic moiety of Y (as forexample -(CH -SO or the anionic moiety of R (as for example -SO exceptthat when Y represents the N-oxide or z is zero X is not required; andwherein it is understood that all unsatisfied valences of carbon atomsare attached to hydrogen atoms, and wherein each vertex of the formulaerepresents a carbon atom.

The following compounds are examples of typical aromatic non-carbonylnitrogen heterocyclic compounds which may be employed according to thisinvention and which illustrate the generalized structural fonnulae givenabove.

p yridine -continued pyridinium chloride propane quinoline 2-quinnlinolBquinolinol 8-quinolinesulfonic acid Nbenzyl-Squinolinesulfonic acidbetaine O M ca,-

quinaldine N-allylquinolinium bromide -continued CH -(E(IH I 2N-propargylisoquinolinium bromide N-benzylisoquinolinium chloride N-(quinaldinyl Hayridinium chloride acridine Some compounds which havegiven particularly outstanding results in fulfilling the objectives ofthis inven- 30 tion are:

4-cyanopyridine 4-cyanopyridine-N-oxide 3-pyridylsulfonic acid2-mercapto-4-methylpyridine 1 ,3-di-(4,4 '-pyridyl)-propane l ,3-di-(4,4-pyridyl-N,N '-oxide)-propane 4,4

p-xylene-a,a'-di-(N,N-pyridinium chloride) N-( 2, 3-dic hloro-2-pr0penyl)-pyridinium chloride N-propargyl-2-( n-propan-3-ol)-pyridinium bromidequinoline N-allylquinolinium bromideN-(2,3-dich1oro-2-propeny1)-quinolinium iodide isoquinolineisoquinoline-Ncxide N-allyisoquinolinium bromide N-benzylisoquinoliniumchloride N-(2,3-dichloro-2-propeny1)isoquinolinium iodide acridine Asingle compound of mixtures of the nitrogen heterocyclic compounds ofthis invention may be used in combination with other additives known tothose skilled in the art of bright zinc plating to overcome depositstriations and/or spores and to generally increase the brightness andenhance the overall appearance and luster of the zinc deposit.

The amount of heterocyclic nitrogen compound or mixtures thereofemployed in the compositions of this invention is an amount sufficientto provide improved bright zinc electroplate when compared with a bathcomposition which is identical in all respects save that said bathcomposition contains no heterocyclic nitrogen compounds of the inventionherein. The improved bright zinc electroplate deposits of the inventionherein are generally characterized as showing improvement in at leastone of the properties such as freedom from dullness or skip in lowercurrent density areas, improved ductility, uniformity of lustrousdeposit throughout the plating current density range and freedom fromspores and/or striations. In general, amounts of heterocyclic nitrogencompounds of about 0.001 g/l 4.0 g/l (preferably about 0.005 0.25 g/l)may be used.

When the aromatic non-carbonyl containing nitrogen heterocycliccompounds of this invention are employed in mildly acidic, neutral, ormildly basic zinc electroplating baths, they are preferably used incombination with carrier and/or support compounds known to those skilledin the art of zinc plating. These carrier and/or support compounds aretypically bath soluble polyethers, substituted polyethers and/orsubstituted nonaromatic nitrogen heterocyclic surfactants.

A bath soluble surfactant which may be employed in amounts of about10-25 g/l (preferably about 2-10 g/l) in combination with the nitrogenheterocyclic compounds in amounts of about 0.001 g1 4.0 g/l (preferablyabout 0.005 0.25 g/l) may include aromatic ethers of aliphaticpolyethers. Preferably the polyether is a polyalkoxylated alkyl phenol.Typical polyalkoxylated alkyl phenols include polyethoxylated alkylphenols having the formula:

wherein R, represents an alkyl group of from 8 to 16 carbon atoms(preferably 8 or 9 carbon atoms) and j is an integer of from 5 to 50(preferably from about 10 to 30), and Q is hydrogen or methyl.

Other polyethers which may be employed in amounts of about 1 .0 25 gll(preferably about 2-10 g/l) in combination with the nitrogenheterocyclic compounds in amounts of about 0.001 4.0 g/l (preferablyabout 0.005 0.25 g/l) may include aliphatic polyethers characterized bythe following general formula:

wherein Q represents hydrogen or methyl and k is an integer of fromabout 7 to 100 (preferably from about 12 to 50).

Other polyethers which may be employed include alkyl polyethers of thegeneral formula:

wherein Q represents hydrogen or methyl and R is an alkyl group of fromabout to 25 carbon atoms and h is an integer from about to 50(preferably about 12 to 25).

Other bath soluble surfactants which may be employed include quaternaryimidazolinium compounds with the following generalized structuralformula:

where R is a saturated or unsaturated fatty acid radical, R is an alkylcarboxylate radical or alkali metal carboxylate, R is an alkyl alcohol,alkyl alcoholate, or ethoxylated alkyl carboxylic acid or alkalie saltthereof, and A is a hydroxyl ion or long chain alkyl sulfate orsulfamate anion.

Other surfactants which may be employed in amounts of about 1.0 25 g/l(preferably about 2 to 10 g/l) in combination with the nitrogenheterocyclic compounds in amounts of about 0.001 4.0 g/l (preferablyabout 0.005 0.25 g/l) include polyvinylpyrrolidone polymerscharacterized by the following general formula:

q where q is an integer of from about 50 to 5000 (preferably from about90 to 3500).

The nitrogen heterocyclic compounds and the polyether compounds used incombination in the novel bright zinc electroplating baths of theinvention may contain inert substituents. By an inert substituent as theterm is used herein is meant any bath compatible group which does notdestroy, reduce, interfere with, or hinder the formation of the brightzinc electrodeposits described herein. Typical examples of inertsubstituents include the halogens (chloride, bromide, iodide, andfluoride); hydroxy groups, alkoxy groups (such as methoxy, ethoxy,propoxy, etc. alkyl groups, sulfate, etc.

According to a particular aspect of the invention, a mixture of thenitrogen heterocyclic compounds and the carrier and/or support compounds(preferably a polyether) may be employed in combination with otheradditives. Examples of such cooperating mixtures include a 50:1 (partsby weight) combination of the reaction products of nonyl phenol withabout 15 moles of ethylene oxide and a nitrogen-containing heterocycliccompound. Other suitable weight ratios of carrier and- /or supportcompounds (polyether) and nitrogen-containing heterocyclic compoundsinclude weight ratios of about :1 to H2: 1 respectively. Mixtures ofnitrogen heterocyclic compounds may also be used and wherever mixturesof nitrogen heterocyclic compounds are employed, the weight ratiosreferred to herein refer to the total weight of all of the nitrogenheterocyclic compounds combined.

The basis metal onto which the bright zinc deposits of this inventionmay be applied may include ferrous metals such as steel and cast iron;copper including its alloys such as brass, bronze, etc.; die cast metalswhich may bear a plate of another metal such as copper; thin coatings,e.g. of silver, nickel, or copper, on a non-conductive article (such asa rigid or flexible plastic) which coating may be applied by chemicalreductive techniques, such as electroless plating, etc.

According to another aspect of the invention the preferred operatingconditions, such as pH, temperature, and current density may varydepending upon the particular bath composition and the nature of thearticle receiving the layer of bright zinc electrodeposit. ln general,good, bright zinc electrodeposits may be obtained within a specificrange of operating conditions. For example, in mildly acid, neutral, ormildly basic zinc baths, when the pH is within the desired range (i.e.about 1.0 10.0, preferably about 4.0 8.0) a zinc electrodeposit mayattain maximum brightness and the current efficiency may also beoptimized.

The bright zinc electroplating processes using the compositions of theinvention may be carried out at temperatures of about 10C. 60C.(preferably 15C. 35C.) either with or without agitation. Using averagecurrent densities of 0.5 5.0 amperes per square decimeter (ASD), brightzinc electrodeposits having average thicknesses of 0.25 25 microns maybe obtained using plating times which may average 0.5 minutes.

If necessary, agitation of the plating bath composition may be providedeither by mechanical movement of the article being plated or by solutionagitation during the electrodeposition. Such agitation may permit theuse of high plating current densities on the article being plated.

During the plating operation, it is desirable to keep metalliccontaminants at very low concentration levels in order to insure abright zinc electrodeposit. Such contamination from metal ions, (such ascadmium, copper, iron, and lead) may be reduced or eliminated throughconventional purification methods. Other types of contaminants (such asorganic contaminants) may also be eliminated or reduced by circulationof the zinc electroplating solution through a suitable filter media suchas activated carbon or types of ion exchange or absorption media.

Some of the nitrogen heterocyclic compounds of this invention may haveonly limited solubility in aqueous solutions. In order to introduce therequired amount of these materials into the plating bath, it is mostadvantageous to first dissolve the appropriate nitrogen heterocycliccompounds in a suitable bath soluble solvent. Such solvents includemethanol, ethanol, isopropanol, ethylene glycol-monoethyl ether (i.e.,cellosolve), acetone, etc. A concentration of about 25 to 50 g/l of theEXAMPLE I A four liter aqueous bright zinc electroplating bathcomposition containing the following ingredients in the amountsindicated was prepared:

ZnCl 40 g/l Nl-LCl I25 g/l citric acid monohydrate 75 g/l NH OH to givea pH of 48 Reaction product of nonylphenol and 15 moles of ethyleneoxide 4 gll 3-pyridylsulfonic acid 0.3 gll Using mild cathode rodagitation, parts were plated in the above bath at an average currentdensity of about 2.5 asd. Excellent, uniformly bright deposits wereobtained which easily accepted a subsequent clear chromate conversioncoating.

EXAMPLE ll An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts indicated:

ZnCl, 32 gll NH,Cl 200 gll pH 5 Reaction product of a mixture of linearsecondary alcohols exhibiting ll to H5 carbon atoms with 12 moles ofethylene oxide 4 gll 2-mercapto-4-methylpyridine 0.04 g/l N2,3-dichloro-2-propenyl isoquinolinium iodide 0.025 gll This bathcomposition was operated in a 267 ml Hull cell at room temperature,using I ampere cell current, a plating time of 5 minutes, mild agitationprovided by a small magnetic stirrer, buffed brass cathodes and a sheetzinc anode. The resultant zinc deposit was bright across the entirecurrent density range of the panel (-6.0 asd.) and was free of highcurrent density spores and/or striations.

EXAM PLE Ill An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts indicated:

ZnCl, 40 gll NH,C1 125 gll citric acid monohydrate 75 Nl-LOH to give pH45 Reaction product of nonylphenol and l moles of ethylene oxide 4 gll3-pyridyl-2-ethylsulfonic 0.4 gll acld d-pyridyl-2-ethylsulfonic-continued acid 0.4 g/l Using a 267 ml Hull cell and the operatingprocedure given in Example II. the resulting zinc deposit was brilliantin the high current density areas, very bright in the medium currentdensity areas and was bright in the low current density areas.

EXAMPLE IV An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts indicated:

ZnCl 32 gll NH,Cl 200 gll pH 4.8 Reaction product of nonylphenol and 15moles of ethylene oxide 4 gll Acridine 0.05 gll 4-cyanopyridine N-oxide0 4 gll Using a 267 ml Hull cell and the operating procedure given inExample 11, the resulting zinc deposit was bright across the entirecurrent density range of the test panel, and was also free of sporesand/or striations.

EXAMPLE V An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts indicated:

ZnCl, 40 gll NH.C| I25 gll citric acid monohydrate gll NH OH sufficientto give pH 4.5

Reaction product of nonylphenol and I5 moles of ethylene oxide 4 g/l l,2di-( 4,4-pyridyl)-ethene 0.04 g/l N-(Z,3-dichloro2-propenyl)-isoquinolinium iodide 0.01 g/l Using a 267 ml Hull cell and theoperating conditions given in Example ll, the resulting zinc deposit wasuniformly bright, spore free and generally excellent across the entirecurrent density range of the test panel.

EXAMPLE Vl An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts indicated:

ZnCl, 4O gll NH,Cl gll citric acid monohydrate 75 gll NH OH sufficientto give pH 75 Reaction product of nonyl phenol and 15 moles of ethyleneoxide 3 gr N-benzylisoquinolinium chloride 0.025 gll Using a 267 ml Hullcell and the operating conditions given in Example [1, the resultingzinc deposit was bright and free of spores across the entire currentdensity range of the test panel.

EXAMPLE VI] A four liter aqueous bright zinc electroplating bathcomposition containing the following ingredients in the amountsindicated was prepared:

ZnCl, 40 g/l NH Cl 125 g/l citric acid monohydrate 75 g/l NH OH toadjust pH to 4.5 Reaction product of nonylphenol and 15 moles ofethylene oxide 4 g/l l ,3-(4,4"dipyridyl)- propane-N.N-dioxide 0.4 g/lN-(2,3-dichloro-2-propenyl)- isoquinolinium iodide 0.01 g/l EXAMPLE VIIIAn aqueous bright zinc electroplating bath composition was preparedusing the following ingredients in the amounts indicated:

zncl 32 g/l Nl-LCI 200 gll pH as prepared 45 Quaternary imidazoliniumcompound sold as Miranol C2M-SF" by the Miranol Chemical Company, Inc.20 g/l N-(2.2-dichloro-2 propenyl)- isoquinolinium iodide 0.025 g/lUsing a 267 ml Hull cell and the operating conditions given in ExampleII, the resulting zinc deposit was uni formly brilliant across theentire current density range of the test panel and was free of sporesand/or striations.

EXAMPLE IX A four liter aqueous bright zinc electroplating bathcomposition containing the following ingredients in the amountsindicated was prepared:

ZnCl 32 g/l NH,CI 200 g/l pH 4.8 Reaction product of nonylphenol and lmoles of ethylene oxide 4 g/l Polyvinylpyrrolidone (M. wt. avg. 40,000)2 g/l N(2,3-dichloro2-propenyl)- isoquinolinium iodide 0.02 g/l Using asmall plexiglass, horizontal, hexagonal plating barrel, 12.5 cm. long bycm. diameter, rotating at about 5 rpm, a large number of barrel loads ofsteel nails (approximately 1000 sq. cm. surface area per load) wereplated in the above bath composition at 10 to amperes cell current for30 minutes. The resulting zinc deposits were brilliant and lustrous asplated, free of any haziness, spores and/or striations. The depositswere subsequently rinsed and given a clear chromate conversion coatingto improve their corrosion resistance as is normal in the zinc platingindustry.

EXAMPLE X A four liter aqueous bright zinc electroplating bathcomposition was prepared using the following ingredients in the amountsindicated:

ZnCl, 32 g/l NH CI 200 g/l pH 4.8 Polyvinylpyrrolidone (M. wt. avg.40,000) 2 g/l Reaction product of nonylphenol and I5 moles of ethyleneoxide 4 g/l N-allylisoquinolinium bromide 0.025 g/l A large number ofparts were rack plated in this bath using cathode rod agitation of about7 meters/min. and an average current density of about 2.0 to 3.0 asd.Plating time ranged from about 30 minutes to 2 hours. Excellent,uniformly brilliant, lustrous zinc deposits, free of haziness, spores orstriations were consistently obtained from this system.

EXAMPLE XI A four liter aqueous bright zinc electroplating bathcomposition containing the following ingredients in the amountsindicated was prepared:

ZnCl, 32 g/l NH,CI 200 g/l pH 4.8 Reaction product of a mixture oflinear secondary alcohols exhibiting ll to lo carbon atoms with 12 molesof ethylene oxide 4 g/l Polyvinylpyrrolidone 2 g/lN-benzylisoquinolinium chloride 0.01 g]! A number of parts were platedin this bath and the resulting deposits were brilliant, lustrous andfree of haze, spores or striations. The average current densities wereabout 2.0 to 3.0 asd.

EXAMPLE XII A four liter aqueous bright zinc electroplating bathcomposition containing the following ingredients in the indicatedamounts was prepared:

ZnCl, 40 gll NI-LCI l25 g/l citric acid monohydrate g/l NH.OH sufficientto give pH 4.5 Reaction product of 1 mole nonylphenol and I5 molesethylene oxide 4 g/l 4-picolylamine 0.2 g]! N( 2 ,3-dichIoro-2-prop enylisoquinolinium iodide 0.01 g]! A number of parts were plated in theabove bath at average current densities ranging from about 1.2 to 3.6amp. per sq. decimeter. After plating, the parts were water rinsed andgiven a clear chromate conversion coating as is the normal practice inthe zinc plating industry. The resulting zinc deposits were uniformlybright and lustrous.

EXAMPLE Xlll An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts indicated:

Using a 267 ml Hull cell and the operating conditions given in Examplell, the resulting zinc deposit was uniformly bright across the entiretest panel and was free of spores and/or striations.

EXAMPLE XIV An aqueous bright zinc electroplating bath composition wasprepared using the following ingredients in the amounts listed:

znso, 714,0

Min 100 g/l Citric acid monohydrate 100 g/l NILOH sufficient to give pH80 Reaction product of nonylphcnol and moles of ethylene oxide 4 g/llsoquinoline-N-oxide monohydratc 0.025 g]! r 24 wherein each R isindependently hydrogen, alkyl, alkenyl, alkoxy, alkylamino,alkylsulfonic acid or salts thereof, sulfonic acid or salts thereof,halogen amino,

5 hydroxyl, mercapto, benzyl, or phenylalkyl Using a 267 ml Hull celland the operating conditions given in Example II, the resulting zincdeposit was lustrous and bright as well as free of striations or sporesacross the entire current density range of the test panel.

Although this invention has been illustrated by reference to specificembodiments, modifications thereof which are clearly within the scope ofthe invention will be apparent to those skilled-in-the-art.

I claim:

l. A method of producing bright, or brilliant zinc electrodeposits freeof spores and/or striations over a wide current density range whichcomprises passing current from an anode to a metal cathode through anaqueous bath composition having a pH of 1.0 to 10.0

and containing at least one zinc compound providing 5 (where m is aninteger 0 to 4); n is an integer 0 to 3; z is 0 or 1; Y is oxygen,allyl, propargyl, benzyl, an alkoxy group, alkyl sulfonic acid -(CH),,-SO (where p is an integer of from 1 to 4), an oxyalkylsulfonic acid,quinaldinyl, p-phenoxybenzyl or a halogenated alkeneyl radical in theabsence of carbonyl and nitrile groups and X represents an anionicradical or the anionic moiety of Y or R provided that when Y is N-oxideX is absent.

2. The method as claimed in claim 1 wherein at least onenitrogen-containing heteroeyclic compound is N- 2, 3-dichloro-2-propenyl)-pyridinium chloride.

3. The method as claimed in claim 1 wherein at least onenitrogen-containing heteroeyclic compound is N- propargyl-2-( n-propan-3-ol )-pyridinium bromide.

4. The method as claimed in claim 1 wherein at least onenitrogen-containing heteroeyclic compound is 2-mercapto-4-methylpyridine.

5. The method as claimed in claim 1 wherein at least onenitrogen-containing heteroeyclic compound is 3- pyridylsulfonic acid.

6. The method as claimed in claim 1 wherein at least one bath-solublesurfactant is a polyether of the formula wherein Q is hydrogen or amethyl group and k is an integer of about 7-l00.

7. The method as claimed in claim 1 wherein at least one bath-solublesurfactant is a polyether of the formula wherein Q is hydrogen ormethyl, R, is alkyl of from 5 to 25 carbon atoms, and h is an integer offrom 10 to 50.

8. The method as claimed in claim 1 wherein at least one bath-solublesurfactant is a quaternary imidazolinium of the formula:

wherein R is a saturated or unsaturated fatty acid radical, R is analkyl carboxylate or alkali metal carboxylate, R is selected from thegroup consisting of alkyl alcoholate, alkyl alcohol, ethoxylated alkylcarboxylic 25 acid and alkali metal salts of ethoxylated alkylcarboxylic acids, and A is a hydroxyl ion or long chain alkyl sulfate orsulfamate anion.

9. A method of producing bright, or brilliant zinc electrodeposits freeof spores and/or striations over a wide current density range whichcomprises passing current from an anode to a metal cathode through anaqueous bath composition having a pH of 1.0 to 10.0 and containing atleast one zinc compound providing zinc ions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and

b. 0.001 gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic [is]compound of the formula (where rn is an integer to 4); n is an integer 0to 3; z is 0 or 1; Y is oxygen, allyl, propargyl, benzyl, an alkoxygroup, alkyl sulfonic acid -(CH ),,-SO (where p is an integer of from 1to 4), an oxyalkylsulfonic acid, quinaldinyl, p-phenoxybenzyl, or ahalogenated alkeneyl radical and X represents an anionic radical or theanionic moiety of Y or R provided that when Y is N-oxide X is absent.

10. The method as claimed in claim 9 wherein at least onenitrogen-containing heterocyclic compound is quinoline.

1 l. The method as claimed in claim 9 wherein at least onenitrogen-containing heterocyclic compound is N- allylquinoliniumbromide.

12. The method as claimed in claim 9 wherein at least onenitrogen-containing heterocyclic compound is N-(2,3-dichloro-2-propenyl)-quinolinium iodide.

13. A method of producing bright, or brilliant zinc electrodeposits freeof spores and/or striations over a wide current density range whichcomprises passing current from an anode to a metal cathode through anaqueous bath composition having a pH of 1.0 to 10.0 and containing atleast one zinc compound providing zinc ions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted 26 polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and b. 0.001 gram per liter to 4.0grams per liter of at least one aromatic, non-carbonyl, non-nitrile, ni-

trogen-containing heterocyclic compound of the formula is Y wherein eachR is independently hydrogen, alkyl, alkenyl, alkoxy, alkylamino,alkylsulfonic acid or salts thereof, sulfonic acid or salts thereof,halogen, amino,

hydroxyl, mercapto, benzyl, or phenylalkyl (where m is an integer 0 to4), n is an integer 0 to 3; R is a divalent alkylene, divalentalkeneylene, secondary amine, or a direct bond between two heterocyclicrings; 2 is 0 or 1; Y is oxygen, allyl, propargyl, benzyl, an alkoxygroup, alkyl sulfonic acid -(CH -SO (where p is an integer of from I to4), an oxyalkylsulfonic acid, quinaldinyl, p-phenoxybenzyl or ahalogenated alkeneyl radical and X represents an anionic radical or theanionic moiety of Y or R provided that when Y is N- oxide X is absent.

14. The method as claimed in claim 13 wherein at least onenitrogen-containing heterocyclic compound is l ,3-di-( 4,4 '-pyridyl-N,N '-oxide )-n-propane.

15. The method as claimed in claim 13 wherein at least onenitrogen-containing heterocyclic compound is 1 ,3-di-(4,4'-pyridyl)propane.

16. A method of producing bright, or brilliant zinc electrodeposits freeof spores and/or striations over a wide current density range whichcomprises passing current from an anode to a metal cathode through anaqueous bath composition having a pH of 1.0 to 10.0 and containing atleast one zinc compound providing zinc ions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and

b. 0.001 gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula n O n 27 wherein each R is independently hydrogen, alkyl,alkenyl, alkoxy, alkylamino, alkylsulfonic acid or salts thereof,sulfonic acid or salts thereof, halogen, amino, hydroxyl, mercapto,benzyl, or phenylalkyl (where m is an integer to 4); n is an integer 0to 3; z is 0 or 1; Y is oxygen, allyl, propargyl, benzyl, an alkoxygroup, alkyl sulfonic acid -(CH ),,-SO (where p is an integer of from 1to 4), an oxyalkylsulfonic acid, quinaldinyl, p-phenoxybenzyl or ahalogenated alkeneyl radical and X represents an anionic radical or theanionic moiety of Y or R provided that when Y is N-oxide X is absent.

17. The method as claimed in claim 16 wherein at least onenitrogen-containing heterocyclic compound is acridine.

18. A method of producing bright, or brilliant zinc electrodeposits freeof spores and/or striations over a wide current density range whichcomprises passing current from an anode to a metal cathode through anaqueous bath composition having a pH of 1.0 to 10.0 and containing atleast one zinc compound providing zinc ions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and I b. 0.001 gram per liter to 4.0grams per liter of at least one aromatic, non-carbonyl, non-nitrile,nitrogen-containing heterocyclic compound of the formula R X X R whereineach R is independently hydrogen, alkyl, alkenyl, alkoxy, alkylamino,alkylsulfonic acid or salts thereof, sulfonic acid or salts thereof,halogen, amino, hydroxyl, mercapto, benzyl, or phenylalkyl (where m isan integer 0 to 4); n is an integer 0 to 3; R" is a bifunctional radicalCH or and X represents an anionic radical or the anionic moiety of R.

19. The method as claimed in claim 18 wherein at least onenitrogen-containing heterocyclic compound isp-xylene-a,a'-di-(N,N'-pyridinium chloride).

20. A composition for providing bright, or brilliant zincelectrodeposits free of spores and/or striations over a wide currentdensity range which comprises an aqueous bath composition having a pH ofl.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers; and

b. 0.001 gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula:

wherein each R is independently hydrogen, alkyl, alkenyl, alkoxy,alkylamino, alkylsulfonic acid or salts thereof, sulfonic acid or saltsthereof, halogen, amino, hydroxyl, mercapto, benzyl, or phenylalkyl(where m is an integer O to 4); n is an integer 0 to 3; z is O or 1; Yis oxygen, allyl, propargyl, benzyl, an alkoxy group, alkyl sulfonicacid -(CH ),-SO (where p is an integer of from 1 to 4), anoxyalkylsulfonic acid, quinaldinyl, p-phenoxybenzyl or a halogenatedalkeneyl radical in the absence of carbonyl and nitrile groups and Xrepresents an anionic radical or the anionic moiety of Y or R providedthat when Y is N-oxide X- is absent.

21. A composition as claimed in claim 20 wherein at least onenitrogen-containing heterocyclic compound isN-(2,3-dichloro-2-propenyl)-pyridinium chloride.

22. A composition as claimed in claim 20 wherein at least onenitrogen-containing heterocyclic compound isN-propargyl-2-(n-propan-S-ol)-pyridinium bromide.

23. A composition as claimed in claim 20 wherein at least onenitrogen-containing heterocyclic compound is2-mercapto-4-methylpyridine.

24. A composition as claimed in claim 20 wherein at least onenitrogen-containing heterocyclic compound is 3-pyridylsulfonic acid.

25. A composition for providing bright, or brilliant zincelectrodeposits free of spores" and/or striations over a wide currentdensity range which comprises an aqueous bath composition having a pH of1.0 to I00 and containing at least one zinc compound providing zinc ionsfor electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and

b. 0.001 gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula:

wherein each R is independently hydrogen, alkyl, alkenyl, alkoxy,alkylamino, alkylsulfonic acid or salts thereof, sulfonic acid or saltsthereof, halogen, amino, hydroxyl, mercapto, benzyl, or phenylalkyl(where m is an integer to 4); n is an integer 0 to 3; z is 0 or 1; Y isoxygen, allyl, propargyl, benzyl, an alkoxy group, alkyl sulfonic acid-(CH ),-SO (where p is an integer of from 1 to 4), an oxyalkylsulfonicacid, quinaldinyl, p-phenoxybenzyl, or a halogenated alkeneyl radicaland X represents an anionic radical or the anionic moiety of Y or Rprovided that when Y is N-oxide X is absent.

26. A composition as claimed in claim 25 wherein at least onenitrogen-containing heterocyclic compound is quinoline.

27. A composition as claimed in claim 25 wherein at least onenitrogen-containing heterocyclic compound is N-allylquinolinium bromide.

28. A composition as claimed in claim 25 wherein at least onenitrogen-containing heterocyclic compound isN-(2,3-dichloro-2-propenyl)-quino|inium iodide.

29. A composition as claimed in claim 25 wherein at least onebath-soluble surfactant is a polyether of the formula:

HO CHCH,Oj H

R,-CH( IH )I wherein Q is hydrogen or methyl, R is alkyl of from 5 to 25carbon atoms, and h is an integer of from to 50.

30 31. A composition as claimed in claim 25 wherein at least onebath-soluble surfactant is a quaternary imidazolinium of the formulaN-CH,

wherein R is a saturated or unsaturated fatty acid radical, R is analkyl carboxylate or alkali metal carboxylate, R is selected from thegroup consisting of alkyl a1- coholate, alkyl alcohol, ethoxylated alkylcarboxylic acid and alkali metal salts of ethoxylated alkyl carboxylicacids, and A is a hydroxyl ion or long chain alkyl sulfate or sulfamateanion.

32. A composition for providing bright, or brilliant zincelectrodeposits free of spores and/or striations over a wide currentdensity range which comprises an aqueous bath composition having a pH of1.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and

b. 0.001 gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula:

RI j N+ E- j- L x x 2 2 wherein each R is independently hydrogen, alkyl,akenyl, alkoxy, alkylamino, alkylsulfonic acid or salts thereof,sulfonic acid or salts thereof, halogen, amino, hydroxyl, mercapto,benzyl, or phenylalkyl (where m is an integer 0 to 4); n is an integer 0to 3; R is a divalent alkylene, divalent alkeneylene, secondary amine,or a direct bond between two heterocyclic rings; 2 is 0 or 1; Y isoxygen, allyl, propargyl, benzyl, an alkoxy group, alkyl sulfonic acid-(CH,),,-SO (where p is an integer of from 1 to 4), an oxyalkylsulfonicacid, quinaldinyl, p-phenoxybenzyl or a halogenated alkeneyl radical andX" represents an anionic radical or the anionic moiety of Y or Rprovided that when Y is N- oxide X is absent.

33. A composition as claimed in claim 32 wherein at least onenitrogen-containing heterocyclic compound is l ,3-di-( 4,4 '-pyridyl-N,N'-oxide )-n-propane.

34. A composition as claimed in claim 32 wherein at least onenitrogen-containing heterocyclic compound is l,3-di-( 4,4 -pyridyl)propane.

35. A composition for providing bright, or brilliant zincelectrodeposits free of spores and/or striations over a wide currentdensity range which comprises an aqueous bath composition having a pH of1.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and

b. 0.00l gram per liter to 4.0 grams per liter of at least one aromatic.non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe wherein each R is independently hydrogen, alkyl, alkenyl, alkoxy,alkylamino, alkylsulfonic acid or salts thereof, sulfonic acid or saltsthereof, halogen, amino, hydroxyl, mercapt, benzyl, or phenylalkyl(where m is an integer to 4); n is an integer 0 to 3; z is 0 or I; Y isoxygen, allyl, propargyl, benzyl, an alkoxy group, allcyl sulfonic acid-(CH,),-SO (where p is an integer of from 1 to 4), an oxyalkylsulfonicacid, quinaldinyl, p-phenoxybenzyl or a halogenated alkeneyl radical andX represents an anionic radical or the anionic moiety of Y or R providedthat when Y is N-oxide X is absent.

36. A composition as claimed in claim 35 wherein at least onenitrogen-containing heterocyclic compound is acridine.

37. A composition for providing bright, or brilliant zincelectrodeposits free of spores and/or striations over a wide currentdensity range which comprises an 32 aqueous bath composition having a pHof 1.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc,

a. 1.0 gram per liter to 25 grams per liter of at least 5 one bathsoluble surfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and b. 0.00] gram per liter to 4.0grams per liter of at least one aromatic, non-carbonyl, non-nitrile, ni-

trogen-containing heterocyclic compound of the formula:

R X X Rn wherein each R is independently hydrogen, alkyl, alkenyl,alkoxy, alkylamino, alkylsulfonic acid or salts thereof, sulfonic acidor salts thereof, halogen, amino, hydroxyl, mercapto, benzyl, orphenylalkyl (where m is an integer 0 to 4); n is an integer 0 to 3; R"

is a bifunctional radical such as

1. A METHOD OF PRODUCING BRIGHT, OR BRILLIANT ZINC ELECTRODEPOSITS FREEOF SPORES AND/OR STRIATIONS OVER A WIDE CURRENT DENSITY RANGE WHICHCOMPRISES PASSING CURRENT FROM AN ANODE TO A METAL CATHODE THROUGH ANAQUEOUS BATH COMPOSITION HAVING A PH OF 1.0 TO 10.0 AND CONTAINING ATLEAST ONE ZINC COMPOUND PROVIDING ZINC IONS FOR ELECTROPLATING ZINC, A.1.0 GRAM PER LITER TO 25 GRAMS PER LITER OF AT LEAST ONE BATH SOLUBLESURFACTANT FROM THE GROUP CONSISTING OF BATH SOLUBLE POLYETHERS,SUBSTITUTED POLYETHERS, AND B. 0.001 GRAM PER LITER TO 4.0 GRAMS PERLITER OF AT LEAST ONE AROMATIC, NON-CARBONYL, NON-NITRILE,NITROGEN-CONTAINING HETEROCYLIC COMPOUND OF THE FORMULA
 2. The method asclaimed in claim 1 wherein at least one nitrogen-containing heterocycliccompound is N-(2,3-dichloro-2-propenyl)-pyridinium chloride.
 3. Themethod as claimed in claim 1 wherein at least one nitrogen-containingheterocyclic compound is N-propargyl-2-(n-propan-3-ol)-pyridiniumbromide.
 4. The method as claimed in claim 1 wherein at least onenitrogen-containing heterocyclic compound is2-mercapto-4-methylpyridine.
 5. The method as claimed in claim 1 whereinat least one nitrogen-containing heterocyclic compound is3-pyridylsulfonic acid.
 6. The method as claimed in claim 1 wherein atleast one bath-soluble surfactant is a polyether of the formula
 7. Themethod as claimed in claim 1 wherein at least one bath-solublesurfactant is a polyether of the formula
 8. The method as claimed inclaim 1 wherein at least one bath-soluble surfactant is a quaternaryimidazolinium of the formula:
 9. A method of producing bright, orbrilliant zinc electrodeposits free of spores and/or striations over awide current density range which comprises passing current from an anodeto a metal cathode through an aqueous bath composition having a pH of1.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc, a. 1.0 gram per liter to 25 grams perliter of at least one bath soluble surfactant selected from the groupconsisting of bath soluble polyethers, substituted polyethers, andsubstituted non-aromatic nitrogen heterocyclic surfactants; and b. 0.001gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula
 10. The method as claimed in claim 9 wherein at least onenitrogen-containing heterocyclic compound is quinoline.
 11. The methodas claimed in claim 9 wherein at least one nitrogen-containingheterocyclic compound is N-allylquinolinium bromide.
 12. The method asclaimed in claim 9 wherein at least one nitrogen-containing heterocycliccompound is N-(2,3-dichloro-2-propenyl)-quinolinium iodide.
 13. A methodof producing bright, or brilliant zinc electrodeposits free of sporesand/or striations over a wide current density range which comprisespassing current from an anode to a metal cathode through an aqueous bathcomposition having a pH of 1.0 to 10.0 and containing at least one zinccompound providing zinc ions for electroplating zinc, a. 1.0 gram perliter to 25 grams per liter of at least one bath soluble surfactantselected from the group consisting of bath soluble polyethers,substituted polyethers, and substituted non-aromatic nitrogenheterocyclic surfactants; and b. 0.001 gram per liter to 4.0 grams perliter of at least one aromatic, non-carbonyl, non-nitrile,nitrogen-containing heterocyclic compound of the formula
 14. The methodas claimed in claim 13 wherein at least one nitrogen-containingheterocyclic compound is 1,3-di-(4,4''-pyridyl-N,N''-oxide)-n-propane.15. The method as claimed in claim 13 wherein at least onenitrogen-containing heterocyclic compound is1,3-di-(4,4''-pyridyl)propane.
 16. A method of producing bright, orbrilliant zinc electrodeposits free of spores and/or striations over awide current density range which comprises passing current from an anodeto a metal cathode through an aqueous bath composition having a pH of1.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc, a. 1.0 gram per liter to 25 grams perliter of at least one bath soluble surfactant selected from the groupconsisting of bath soluble polyethers, substituted polyethers, andsubstituted non-aromatic nitrogen heterocyclic surfactants; and b. 0.001gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula
 17. The method as claimed in claim 16 wherein at least onenitrogen-containing heterocyclic compound is acridine.
 18. A method ofproducing bright, or brilliant zinc electrodeposits free of sporesand/or striations over a wide current density range which comprisespassing current from an anode to a metal cathode through an aqueous bathcomposition having a pH of 1.0 to 10.0 and containing at least one zinccompound providing zinc ions for electroplating zinc, a. 1.0 gram perliter to 25 grams per liter of at least one bath soluble surfactantselected from the group consisting of bath soluble polyethers,substituted polyethers, and substituted non-aromatic nitrogenheterocyclic surfactants; and b. 0.001 gram per liter to 4.0 grams perliter of at least one aromatic, non-carbonyl, non-nitrile,nitrogen-containing heterocyclic compound of the formula
 19. The methodas claimed in claim 18 wherein at least one nitrogen-containingheterocyclic compound is p-xylene- Alpha , Alpha ''-di-(N,N''-pyridiniumchloride).
 20. A composition for providing bright, or brilliant zincelectrodeposits free of spores and/or striations over a wide currentdensity range which comprises an aqueous bath composition having a pH of1.0 to 10.0 and containing at least one zinc compound providing zincions for electroplating zinc, a. 1.0 gram per liter to 25 grams perliter of at least one bath soluble surfactant selected from the groupconsisting of bath soluble polyethers, substituted polyethers; and b.0.001 gram per liter to 4.0 grams per liter of at least one aromatic,non-carbonyl, non-nitrile, nitrogen-containing heterocyclic compound ofthe formula:
 21. A composition as claimed in claim 20 wherein at leastone nitrogen-containing heterocyclic compound isN-(2,3-dichloro-2-propenyl)-pyridinium chloride.
 22. A composition asclaimed in claim 20 wherein at least one nitrogen-containingheterocyclic compound is N-propargyl-2-(n-propan-3-ol)-pyridiniumbromide.
 23. A composition as claimed in claim 20 wherein at least onenitrogen-containing heterocyclic compound is2-mercapto-4-methylpyridine.
 24. A composition as claimed in claim 20wherein at least one nitrogen-containing heterocyclic compound is3-pyridylsulfonic acid.
 25. A composition for providing bright, orbrilliant zinc electrodeposits free of ''''spores'''' and/or striationsover a wide current density range which comprises an aqueous bathcomposition having a pH of 1.0 to 10.0 and containing at least one zinccompound providing zinc ions for electroplating zinc, a. 1.0 gram perliter to 25 grams per liter of at least one bath soluble surfactantselected from the group consisting of bath soluble polyethers,substituted polyethers, and substituted non-aromatic nitrogenheterocyclic surfactants; and b. 0.001 gram per liter to 4.0 grams perliter of at least one aromatic, non-carbonyl, non-nitrile,nitrogen-containing heterocyclic compound of the formula:
 26. Acomposition as claimed in claim 25 wherein at least onenitrogen-containing heterocyclic compound is quinoline.
 27. Acomposition as claimed in claim 25 wherein at least onenitrogen-containing heterocyclic compound is N-allylquinolinium bromide.28. A composition as claimed in claim 25 wherein at least onenitrogen-containing heterocyclic compound isN-(2,3-dichloro-2-propenyl)-quinolinium iodide.
 29. A composition asclaimed in claim 25 wherein at least one bath-soluble surfactant is apolyether of the formula:
 30. A composition as claimed in claim 25wherein at least one bath-soluble surfactant is a polyether of theformula:
 31. A composition as claimed in claim 25 wherein at least onebath-soluble surfactant is a quaternary imidazolinium of the formula 32.A composition for providing bright, or brilliant zinc electrodepositsfree of spores and/or striations over a wide current density range whichcomprises an aqueous bath composition having a pH of 1.0 to 10.0 andcontaining at least one zinc compound providing zinc ions forelectroplating zinc, a. 1.0 gram per liter to 25 grams per liter of atleast one bath soluble surfactant selected from the group consisting ofbath soluble polyethers, substituted polyethers, and substitutednon-aromatic nitrogen heterocyclic surfactants; and b. 0.001 gram perliter to 4.0 grams per liter of at least one aromatic, non-carbonyl,non-nitrile, nitrogen-containing heterocyclic compound of the formula:33. A composition as claimed in claim 32 wherein at least onenitrogen-containing heterocyclic compound is1,3-di-(4,4''-pyridyl-N,N''-oxide)-n-propane.
 34. A composition asclaimed in claim 32 wherein at least one nitrogen-containingheterocyclic compound is 1,3-di-(4,4''-pyridyl)propane.
 35. Acomposition for providing bright, or brilliant zinc electrodeposits freeof spores and/or striations over a wide current density range whichcomprises an aqueous bath composition having a pH of 1.0 to 10.0 andcontaining at least one zinc compound providing zinc ions forelectroplating zinc, a. 1.0 gram per liter to 25 grams per liter of atleast one bath soluble surfactant selected from the group consisting ofbath soluble polyethers, substituted polyethers, and substitutednon-aromatic nitrogen heterocyclic surfactants; and b. 0.001 gram perliter to 4.0 grams per liter of at least one aromatic, non-carbonyl,non-nitrile, nitrogen-containing heterocyclic compound of the formula:36. A composition as claimed in claim 35 wherein at least onenitrogen-containing heterocyclic compound is acridine.
 37. A compositionfor providing bright, or brilliant zinc electrodeposits free of sporesand/or striations over a wide current density range which comprises anaqueous bath composition having a pH of 1.0 to 10.0 and containing atleast one zinc compound providing zinc ions for electroplating zinc, a.1.0 gram per liter to 25 grams per liter of at least one bath solublesurfactant selected from the group consisting of bath solublepolyethers, substituted polyethers, and substituted non-aromaticnitrogen heterocyclic surfactants; and b. 0.001 gram per liter to 4.0grams per liter of at least one aromatic, non-carbonyl, non-nitrile,nitrogen-containing heterocyclic compound of the formula:
 38. Acomposition as claimed in claim 37 wherein at least onenitrogen-containing heterocyclic compound is p-xylene- Alpha , Alpha''-di-(N,N''-pyridinium chlorIde).